Take your time before answering, if you want. I know I will.
While you're cogitating, you might check out The Replacement Level Yankees blog, where they've run 3000 hypothetical 2006 seasons by Diamond Mind, and come up with some conclusions.
Basically, he's got the Astros finishing fourth, but these are the same kind of simulations that had the Cards sweeping last year's NLCS.
So I can't say I'm all that worried. But it does point out that what we may be seeing over the next few weeks as the predictions from the pundits come in, is that, other than maybe the '98 Marlins, the Astros will be one of the least respected defending NL champs in recent memory.